Clutch hydraulic system not functioning, frustrated. *Update 1/5

[Robw_z]

Welcome to my office:

I began having trouble getting into first and reverse. Turn engine off, no problem shifting, so clutch is not disengaging.

I suspected the clutch clevis pin, removed dash and indeed, it is bad. Replaced with some welding and GoWesty clevis pin kit.

To my surprise, shifting does not improve so I fooled around with the threaded rod between the clevis pin and the clutch master cylinder. This was to no avail, no improvement.

I then replaced the clutch master cylinder with a new unit. Much, much, much bleeding later it finally works. I have pressure like I haven't felt in a long time and I can shift fine, go to bed happy.

Next day the situation is worse than before. Day after almost no pressure at all. I suspected the copper ring seals at the master cylinder(I believe these are specific to later model years, I have a 1990). Hard to find replacements, so I removed, cleaned, flipped them around, no improvement.

Perhaps the extra pressure blew out the slave cylinder, so I replaced the slave cylinder with a new unit. No improvement.

I have pressure bled the system forward and backward, going through two full quarts of dot 4 brake fluid. No improvement.

Either the copper sealing rings really need to be brand new, which I doubt, or one of the new master/slave units is bad. Both are FTE brand.

So I suppose my question is, if one of them is bad, why aren't they leaking? Can a master or slave fail internally and the piston just lets the fluid slip past it?

Final Note: I observed while pushing on the brake pedal, which has very good pressure, the fluid level in the brake reservoir drops, and then increases when the pedal is released. This is only notable when the fluid in the reservoir is at the tippy top.

When pushing on the clutch pedal, the fluid in the reservoir increases, and then goes back down when released.

So frustrated, might as well start bathing in and drinking brake fluid now as I'm going insane.

-Rob

[macjack]

Sorry to hear of your saga, Robw_z.
You've gotten further into your clutch issue than I, so I won't have much useful to add, except camaraderie. And it sounds like the potential valving between the clutch and brake hydraulics is next?
_________________
87 TDI Syncro Westy
81 Westy (sold)
80 Rabbit Wolfsburg (rolled)
Bike as primary transportation

[Ahwahnee]

[E1]

To All at Large, could air in the system(s) make fluid level rise in the master?

OP, are you dead sure there's no air, and/or no way for air to keep coming in?

Potentially related, we currently have an issue downshifting from 4th to 3rd. (Good) Mechanic thinks it's the shift bits at the base of gearshift lever, will know Friday...
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Robw_z]

I am going to replace the clutch master, again, and see what happens.

-Rob

[SyncroButter]

Did you bench bleed the master cylinder and then seal it up well before installing it? The last time I did a master cylinder this was required, but that was also before I owned a power bleeder so your mileage may vary.
_________________
Grant
In the stable: 1986 Syncro Westfalia/Bostig, 1989 Doka Tristar, 1974 Vespa Rally 200, 1973 Vespa Primavera 125, 1963 Solex 2200, 1938 Buick Special
Gone but not forgotten: 1989 Porsche 944, 1973 Standard Beetle

[Gizmoman]

[dobryan]

Can you have a helper press on the clutch while you watch the slave to make sure it is operating all the way? Does sound like a bad master or slave.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[Robw_z]

[Robw_z]

[Bub]

To judge the clutch hydraulic action can't you have someone operate the clutch pedal while you watch the slave cylinder in the back? (like @Dobryan said)
That would give you an idea if things are physically working; the throw is a couple inches.
I know the fluid level in the reservoir can go up and down as you operate the clutch, so does sound like it could be the clutch master. At that point you could do a little old fashioned bleeding at the slave and tell if it's working.
There's also the rubber/ flexible clutch line by the trans; if it is failing/ corroded internally it can swell as pressure builds and cause a spongy pedal.
_________________

[?Waldo?]

[E1]

Per adding yet another master, I'd be shocked if throwing parts at this problem proves fruitful.

Bleed a quart or more through your brakes until it runs dead clear, then do same with clutch. Beyond filth, air is either getting in there, or is still in there.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[SyncroButter]

[E1]

[Robw_z]

Update:

before replacing the M/C, I fooled around with the rod above it. All I can do is back it up to where the threads are dirty(ie where it was factory) and then a bit more. The Bentley specifies 0.5mm between the rod and piston but it is not possible to measure this without removing the assembly which requires removing the dash. It does have more free play now, which is what I was going for to eliminate any "perennial depression" of the M/C piston. I bled it a lot still no go.

I got a new master cylinder and installed it, this time with new copper rings.

Huge amount of bleeding later, no better, the clutch will still not disengage. With the engine running pushing on the clutch makes a subtle noise, probably the noise of a slightly but not fully disengaged clutch.

If it was a clutch or clutch fork, or even throwout bearing issue back at the transmission, wouldn't the pedal still feel good? That shouldn't affect hydraulic pressure. I took a video of the clutch action, and it looks like I thought it would, the lever going down but not all the way.


Link


The transmission was rebuilt 50k ago and the clutch was replaced at that time.

In almost 20 years of VW ownership this is the first time I've been defeated. I may have to call a tow truck to bring it to a shop.

Dumbfounded.

-Rob[/youtube]

[?Waldo?]

[Gizmoman]

[Robw_z]

The only reason I’m doubting a clutch or fork issue is because of that magical test drive a week ago where it was working just fine.

All I can think to do is perhaps use a ratchet strap or something to pull the clutch lever to maximum. If I can’t shift at that point, it isn’t the fault of the hydraulics.

I just know it’s going to be a real pain to put that theory into practice though.

-Rob

[dobryan]

Hmmm Good idea on pulling the clutch lever.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794